1. Field of the Invention
This invention relates in general to a writing method for an optical disc, a processing method for information, an optical disc apparatus, and an information processing apparatus.
2. Description of Related Art
Conventionally, a spiral track is formed on a compact disc (CD) from the inner circumference to the outer circumference. In addition, an example for a data recordable disc is a CD-R (Compact Disc-Recordable) disc. When data is written to the CD-R disc, data is also written on the track with a constant linear density.
In general, the optical disc device for writing information on a writing medium, such as a CD-R/RW (Compact Disc-Recordable/ReWritable) medium having a spiral track thereon, is rotated under a CLV (Constant Linear Velocity) control. For the CLV control, the optical disc is controlled to rotate with a rotational velocity such that the track length passing over an optical pick-up of the optical disc device per unit time is a constant. Therefore, when information is recorded on the inner circumference of the recording medium, the rotational speed of the recording medium is faster, while when information is recorded on the outer circumference of the recording medium, the rotational speed is slower.
As the optical disc apparatus, such as the CD-R/RW, for writing information to an optical disc is used as an external apparatus of a personal computer and becomes popular, a high-speed writing is greatly desired. When the optical disc is written with a high speed, the rotational speed of the optical disc becomes large. Due to influences of the bad mechanical accuracy, the wobbling surface of the optical disc and the eccentricity, etc., a track deviation, which means that the light spot for writing data to the optical disc falls out of the track, occurs easily. When the track deviation occurs during the data writing, the optical disc cannot be used any more. This is a severe problem.
For the CD-R disc, the data writing density of the entire disc surface is the same. When the linear velocity (a relative velocity along the tangent direction of the light spot position on the optical disc) of the light spot for writing/reproducing data on the optical disc is fixed at 1.2 to 1.4 m/s, the channel bit rate of data is 4.3218 MB/sec. The writing speed under such a condition is known as a 1× writing speed, and the optical disc controlled to rotate with a constant linear velocity is known as a CLV (constant linear velocity) writing. Because the CD type disc uses the format above that the linear velocity of data is constant, the writing is performed by the CLV method. Based on the one time speed (1×), the CLV writing is performed with an integer time speed (such as 1×, 2×, 4×, 8×, 12×, 16×, 20×, etc, × is a multiple).
When the data writing is performed by the CLV method, the number of rotations of the optical disc at the inner circumference and the number of rotations of the optical disc at the outer circumference are greatly different. Of course, the number of rotations of the optical disc at the inner circumference is greater than the number of rotations of the optical disc at the outer circumference. In order to suppress the occurrence of the track deviation during the data writing, the entire optical disc has to be written by setting a CLV speed such that the track deviation will not occur at the innerest circumference where the optical disc rotates with a highest speed. In this situation, the number of rotations at the outer circumference of the optical disc has a margin with respect to the track deviation.
In addition to the CLV control, there is still a CAV (Constant Angular Velocity) control such that the optical disc is controlled to rotate with a constant angular velocity. For the CAV control, information is always recorded to the recording medium with a constant rotational velocity of the recording medium, rather than according to a writing position of the recording medium with respect to the optical pick-up.
Recently, the optical disc has become highly competitive in the high-speed application. Because of a spindle motor that drives the optical disc, a high-speed rotation is necessary. For the CLV optical disc, in view of the spindle motor, the optical pick-up has to rotate fast when information is recorded on the inner circumference of the recording medium, and the rotational speed of the recording medium is faster, while the optical pick-up can rotate slowly when information is recorded on the outer circumference of the recording medium. To increase the speed of the spindle motor requires using a motor, a driver, and circuits for the high-speed demand. Accordingly, it is obvious that the system itself becomes larger and the cost goes up.
To solve the above problems, a ZCLV (Zoned CLV) control is made practicable. For the ZCLV control, the writing speed at the inner circumference of the recording medium (the optical disc) is slowed. When information is recorded on an outer circumference from certain position of the recording medium, the writing speed is increased. Namely, when information is recorded on the innermost circumference of the recording medium, the spindle motor rotates with a high speed. Therefore, as the writing position is moved to the outer circumference of the recording medium, the rotation of the spindle motor is continuously slowed because of the CLV control.
According to the ZCLV method, the writing area of the optical disc is divided into zones, such as the inner circumference, the middle circumference and the outer circumference, the CLV writing speed for each zone is set such that a continuous writing is made possible, by which the mechanism can implement a high-speed writing. FIG. 2 shows an example for implementing the ZCLV writing according to the above technology. In FIG. 2, the horizontal axis stands for the position (time) of the optical disc and the vertical axis stands for the writing speed. In this example, the optical disc is divided into three zones (Lead-In to t1, t1 to t2, and t2 to Lead-Out), and the CLV velocities for the tree zones are set to S1, S2 and S3, respectively for writing data. At the zone joint t1, t2, a technology disclosed by Japanese Laid Open H10-49990 can be used to maintain the data continuity.
For the general CLV method, the rotational speed of the spindle motor is continuously decreased from the innermost circumference to the outermost circumference. However, for the ZCLV method, once the writing is interrupted at a certain position, the writing speed is increased. Namely, the rotational speed of the spindle motor is increased at that position. As the rotational speed of the spindle motor is increased, the writing is restarted. Then, information is written to the optical disc toward the outer circumference and the rotational speed of the spindle motor is continuously decreased during this period. By repeatedly performing the process for a predetermined time, the spindle motor can rotate with a higher speed until data is written to the outer circumference of the optical disc.
In addition, because the density of information written to the optical disc of the entire track is the same, the track length passing over the optical pick-up per unit time is easily understood. Assuming the writing speed from the inner circumference to the outer circumference of the optical disc is increased twice, the relationship between the writing position on the disc and the rotational speed of the spindle motor is shown in FIG. 2. In the above ZCLV method, the upper limit of the rotational speed of the spindle motor can be put to a certain value and a higher writing speed is possible.
Conventionally an optical disc writing method for optimizing the writing speed is provided. The spiral track on the optical disc is divided into a plurality of zones, and the data writing to each zone is performed with a different CLV writing speed. In the ZCLV writing method, a plurality of writing modes is set. In each writing mode, zone dividing times for dividing the zones and CLV writing speeds for each of zones are used as zone parameters and stored in a memory. Before writing, the type of the optical disc is determined by a disc-type determining device, and according to result, the zone parameters suitable for the disc type are selected among the plurality of zone parameters from the memory. Then, the ZCLV writing is performed under a writing mode corresponding to the selected zone parameters.
Japanese Laid Open H07-93873 or H11-66726 discloses a writing method by the ZCLV method for an optical disc where zones exist. Regarding this method, for an optical disc consisting of only one spiral track, such as the CD-R disc, because the zones are not divided in advance, the ZCLV writing cannot be used.
For the ZCLV method, because the optical discs are made by different corporations and countries, their characteristics, such as the eccentricity and the burred surface, are also different. When an optical disc with bad characteristic is used in the disc apparatus and the rotates with a high speed, the follow controls of the focusing servo and the tracking servo will fail and the data writing cannot be performed with a high writing speed. In the above writing method, when the optical disc to which data is written cannot be written with a high writing speed, this situation will be detected so that the zone parameters, which are capable of writing data with a highest speed among all possible writing speeds for the optical disc, can be selected among the finite number of the zone parameters stored in the memory.
In the optical disc apparatus, the writing power is different and dependent on the type of the optical disc. The reason is that the writing characteristic is greatly different due to the different material of the recording film, the film pressure, and the physical aspects of the width and the depth of the track, etc. In order to match the writing characteristic of the optical disc, the width of the writing pulse is adjusted for each type of optical disc.
In addition, the writing power is also different according to the CLV speed during the data writing. In general, if the writing power is proportional to the root of the CLV speed, the width of the writing pulse is adjusted for each type of optical disc. The writing power varies with and greatly depends on the disc type and the CLV speed.
In addition, the mechanical characteristic is also different according to the disc type because of the sputtering accuracy, the punching accuracy and the process manage target etc that the disc maker uses. If the mechanical characteristic of the optical disc is worse, there is danger due to the track deviation when the optical disc rotates with a high speed. When the high-speed writing is performed by the ZCLV method, it has to avoid the writing interrupt due to the track deviation. Therefore, the writing speed has to be determined according to a trade-off with the mechanical characteristic of the optical disc.
Considering the mechanical variations due to the disc type, it becomes a problem to provide a method for determining the zone region t1, t2, and their corresponding CLV speed (writing speed) such that the data writing to the optical disc can be performed with a highest speed and a highly reliable writing without track deviation can be performed to the optical disc.
Even if the optical discs are the same type, the writing sensitivity and the mechanical characteristic are dispersed due to the unevenness of the manufacturing conditions. Regarding the optical disc apparatus, because of the unevenness of the assemble accuracy, the chucking accuracy (a shifting amount between the center of the optical disc and the rotational center of the driving motor) when the optical disc is loaded is also uneven, and the relative mechanical accuracy of the optical disc becomes uneven too. In addition, due to the unevenness of the wavelength of the semiconductor laser, the writing sensitive characteristic is also uneven. Due to the unevenness of the manufacturing conditions, the maximum possible writing speed is also uneven. To really detect the variation of the maximum writing speed due to the manufacture unevenness, the maximum writing speed has to be set.
According to above writing method, the number of the zone parameters stored in the memory is finite. The zone parameters are only generated on an assumption of several parameters. As for the optical disc, even though the zone parameters have a writable speed without causing the track deviation, it cannot be used as zone parameters capable of performing at highest writing speed.
When the optimum writing speed is determined and set by the optical disc apparatus, the data writing to the optical disc will be performed with a speed different from the speed that is set with a writing software by the user. At this time, when the writing speed is lower than the writing speed set by the user, the writing operation does not complete even though the preset writing time has passed, the ill condition for the optical disc apparatus occurs and the personal computer may hang up.
When the optimum writing speed is determined and set by the optical disc apparatus, the data writing to the optical disc will be performed with a speed different from the speed that is set with a writing software by the user. At this time, the preset writing complete time is unknown. In addition, the user cannot set the writing speed to try to use the optical disc apparatus. For example, if the user has many of the same optical discs, the limit of the writing speed cannot be found by experiment.